An engine may include a plurality of cylinders to combust fuel and deliver propulsive power to a vehicle. All cylinders of an engine may be configured to have a same compression ratio, but all of the cylinders may not have a same compression ratio due to piston to cylinder clearance variation, piston dimensional variations, and other conditions. The compression ratio differences may affect peak cylinder pressures when the engine is combusting fuel, and variation of cylinder pressure from a desired cylinder pressure may reduce engine fuel economy, reduce engine torque, and reduce engine output power. Thus, it may be desirable to determine and control pressures in cylinders to improve engine performance and emissions. One way to determine pressures in engine cylinders is to install a pressure sensor in each engine cylinder. However, adding a pressure sensor to each engine cylinder can increase engine cost. Therefore, it may be desirable to provide a way of determining cylinder pressure without having to install a pressure sensor in each engine cylinder.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine operating method, comprising: adjusting a cylinder pressure control actuator of an engine via a controller based on a cylinder compression ratio estimated from a deceleration rate of the engine.
By adjusting a cylinder pressure actuator based on a compression ratio estimated from a deceleration rate of an engine, it may be possible to provide the technical result of optimizing engine cylinder pressure control without having to install a pressure sensor in each cylinder. In particular, one engine cylinder may be instrumented with a pressure sensor while all other engine cylinders do not have pressure sensors. The one cylinder that has the pressure sensor may be referred to as a reference cylinder. A deceleration rate of the engine during a compression stroke of the reference cylinder may allow pressure in the reference cylinder and compression ratio of the reference cylinder to be correlated to the deceleration rate of the engine during the compression stroke of the reference cylinder. The correlation may be expressed as a compression factor and deceleration rates observed during compression strokes of other engine cylinders may then be related to the relationship between engine deceleration rate and cylinder pressure for the reference cylinder to determine compression factors for the other cylinders that do not include pressure sensors. The compression factors for the cylinders that do not include pressure sensors may provide a basis for adjustments that affect cylinder pressure in the cylinders without pressure sensors. For example, start of fuel injection time for a cylinder during an engine cycle, end of fuel injection time for the cylinder during the engine cycle, and amount of fuel injected to the cylinder during the engine cycle may be adjusted to control pressure in a cylinder without a pressure sensor to optimize engine power, torque, and fuel economy.
The present description may provide several advantages. In particular, the approach may improve pressure control for engine cylinders. In addition, the approach may be applied at a lower cost than approaches where a pressure sensor is included in each engine cylinder. Further, the approach may improve engine power, fuel economy, and torque.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.